1. Field of the Invention
The present invention relates to an enhanced 8-VSB reception system and E8-VSB data demultiplexing method, by which a plurality of enhanced data, which are encoded at different code rates and are multiplexed with MPEG data encoded by the previous ATSC 8VSB system to be transmitted, can be received.
2. Discussion of the Related Art
Generally, the United States of America (U.S.A.) has adopted the ATSC (advanced television systems committee) 8VSB (vestigial sideband) transmission system as standards for terrestrial digital broadcasting in 1995 and has started the broadcasting since 1998. The Republic of Korea has adopted the standards of the ATSC 8VSB transmission system and has started its experimental broadcasting on May, 1995. The experimental broadcasting was switched to test broadcasting systems on Aug. 31, 2000, and the regular broadcasting has been broadcasted by major broadcasting stations since October, 2001.
FIG. 1 is a block diagram of an ATSC 8VSB transmission system according to a related art. Referring to FIG. 1, an ATSC data randomizer 101 randomizes inputted MPEG video/voice data to output to a Reed-Solomon coder 102. The Reed-Solomon coder 102 performs Reed-Solomon coding on the randomized data, adds 20-byte parity code to the coded data, and then outputs the corresponding data to a data interleaver 103. The data interleaver 103 performs interleaving on the data outputted from the Reed-Solomon coder 102 to change a sequence of the data and then outputs the interleaved data to a trellis coder 104. The trellis coder 104 converts the interleaved data to symbols from bytes and then performs trellis coding on the converted data to output to a multiplexer 105. The multiplexer 105 multiplexes a trellis-coded symbol column with sync signals to output to a pilot inserter 106. The pilot inserter 106 adds a pilot signal to the multiplexed symbol column to output to a VSB modulator 107. The VSB modulator 107 modulates the symbol column outputted from the pilot inserter 106 into an 8VSB signal of an intermediate frequency band to output to an RF converter 108. And, the RF converter 108 converts the received 8VSB signal of the intermediate frequency band to an RF band signal to transmit via antenna.
The ATSC 8VSB transmission system developed for the HID (high definition) broadcast transmits MPEG-2 digital video and Dolby digital sound. Recently, as the Internet globally prevails in use, the demand for interactive broadcast is rising, and various supplementary services are requested. In order to meet such demands, many efforts are made to develop the system enabling to provide separate supplementary services as well as the MPEG-2 digital video and Dolby digital sound on the same channel.
In this case, unlike the normal video/sound data, the supplementary data such as a program execution file, stock information, and the like should be transmitted with a lower error rate. In case of the video/sound data, errors failing to be perceptible to human eyes and ears are no big deal. Yet, in case of the supplementary data, one bit error occurrence may raise a serious problem.
Hence, in a new E8-VSB transmission system compatible with the previous ATSC 8VS system, supplementary data are coded by ½ and ¼ code rates, respectively, the supplementary data are multiplexed by 164-byte packet unit according to a previously determined multiplexing format, the multiplexed data are further pre-processed to output as an MPEG transport packet format, the pre-processed enhanced data are multiplexed by 188-byte packet unit according to the previously determined multiplexing format, and the multiplexed data by 188-byte packet unit are then transmitted. Such technology has been filed by the present applicant (Korean Patent Application No. 10-2003-0017834, filed on Mar. 21, 2003).
In the applicant's previous patent application, data are divided into main data and enhanced data. The main data mean the foregoing-explained previous MPEG-2 video and Dolby digital sound data. And, the enhanced data mean ½ enhanced data coded at ½ code rate and ¼ enhanced data coded at ¼ code rate. In the applicant's previous patent application, the ½ enhanced data and the ¼ enhanced data are called ½ supplementary data and ¼ supplementary data, respectively. Yet, their meanings are identical to each other.
For convenience of explanation in the following description, as explained in applicant's previous patent application, a transmitted signal resulting from multiplexing enhanced data and main data (or normal data) is called an enhanced 8-VSB (hereinafter abbreviated E8-VSB) signal. Besides, the enhanced data and the main data can be used as the enhanced data and the main data, respectively.
FIG. 2 is a block diagram of a general ATSC 8VSB receiver.
Referring to FIG. 2, once a VSB-modulated RF signal is received via antenna, an RF tuner 201 selects an RF signal of a specific channel only by tuning and then converts it to an IF signal to output to an IF mixer 202. The IF mixer 202 down-coverts the IF signal outputted from the tuner 201 to a near baseband (BB) signal to output to a demodulator 203. The demodulator 203 performs VSB demodulation on the near BB signal to output to an equalizer 204.
The equalizer 204 compensates channel distortion included in the VSB-demodulated signal to output to an 8VSB channel decoder 205. The 8VSB channel decoder 205 converts the channel distortion compensated signal to an MPEG transport (TP) type signal to output.
However, in the general ATSC 8VSB receiver shown in FIG. 2, in case that the E8-VSB signal corresponding to the multiplexed signal of the enhanced data and the main data is transmitted, the enhanced data packets will be recognized as null packets via PID (Packet Identification) of MPEG transport header and gracefully discarded. Therefore the legacy ATSC 8-VSB receiver will receive the main data and discard the enhanced data as null packets.